Yeap... a digital pot would be the way to go... though you'd first have to convert the signal using an ADC, then have a microcontroller communicate with the digpot to tell it what value to use. Some MCUs out there already have an ADC embedded in them... you'd have to check and see.Digital potentiometer.
Maybe, maybe not. If this is a sender unit for a tank that he is using to water his geraniums would it be forbidden?Isn't this just another gas gauge sender project and thus a forbidden topic here?
Only if the tank is his radiator. And the radiator is on an automobile. For some reason a generator's radiator seems ok to mods.Maybe, maybe not. If this is a sender unit for a tank that he is using to water his geraniums would it be forbidden?
Exaxtly. This is a tank level probe on a tractor design I'm working on. I measured the current values at 0 and 5v, but I don't understand how I can go to my analog gauge with this...?It would likely be easier to determine what current the 30-212 ohms resistance corresponds to and convert the 0-5V to that current. I assume this is to drive a tank level analog gauge that normally responds to a resistance value in series with it.
Exaxtly. This is a tank level probe on a tractor design I'm working on. I measured the current values at 0 and 5v, but I don't understand how I can go to my analog gauge with this...?
The way you are looking at this is a bit upside-down. Can you start over and explain that you have a sender unit. It puts out zero to 5 volts. I understand that. What I don't understand is, why don't you just measure the 0 to 5 volts with something like, say, a volt meter? No current needs to flow (unless you have an open collector output).I have a sender unit that outputs 0-5v. (0 for empty to 5v for full) I need to build a circuit or use some device that will convert this range to a 30-212ohm resistance. Is this possible? (Pots. do exactly the opposite)
Can the 9V supply be upgraded to something like 13V, similar to the gauge voltage supply, with some minor changes?Here's the basis of how you could do it the good old analogue way:-
View attachment 76652
The vertical axis volts simulate the synthesised resistance Ohms as seen by the gauge. The horizontal axis represents the sender signal. Trim1 sets the 30Ω limit and Trim2 sets the 212Ω limit. Resistor values may need to be tweaked, depending on the gauge internal resistance.
B1 in the sim divides the FET drain voltage by drain current, merely for displaying the synthesised resistance.
Opamp and NFET type are not critical.
I don't see why you couldn't add a 7809 regulator to the circuit, and get a 9V output from your 13V sourceCan the 9V supply be upgraded to something like 13V, similar to the gauge voltage supply, with some minor changes?
Not with minor changes. But why would you want to? The circuit needs a stable voltage, which the 13V supply is presumed not to be. A 7809, as represented by the 9V source in the sim, can provide the stable voltage from a varying 12V or greater supply.Can the 9V supply be upgraded to something like 13V, similar to the gauge voltage supply, with some minor changes?
Its just lack of experience and now I understand this. Overall, I like the design a lot. If I had these components on hand, then I would have tried to build it. At this point, I'm either going to get rid of the gauge and build a level gauge using a led driver lm3914 that displays a level from 0-5v or build and test your circuit design. The response curve also helps and should work pretty well in my application. Thanks for the post and circuit design, Ill try to follow up as things progress.Not with minor changes. But why would you want to? The circuit needs a stable voltage, which the 13V supply is presumed not to be. A 7809, as represented by the 9V source in the sim, can provide the stable voltage from a varying 12V or greater supply.